Waterjet control systems

ABSTRACT

A dual axis joystick control system is used intuitively for manoeuvring a waterborne vessel having two or more waterjets with steering deflectors ( 13 ) and reverse ducts ( 14 ) mounted independently of the steering deflectors. The joystick ( 21 ) is operated to actuate the reverse ducts of the port and starboard waterjets for either common or differential deflections of thrust, and to actuate the steering deflectors of the port and starboard waterjets for common deflections of thrust.

FIELD OF THE INVENTION

This invention relates generally to control systems for waterbornevessels which are of propelled by waterjets. In particular but notsolely the invention relates to systems for manoeuvring vessels havingtwo or more waterjets with steering deflectors, and reverse ducts whichare mounted independently of the steering deflectors. These systemsenable use of a dual axis joystick controller to carry out a wide rangeof manoeuvres.

BACKGROUND OF THE INVENTION

A waterjet propulsion unit for a waterborne vessel produces thrust byway of a reaction to discharge of a high speed jet stream from an enginedriven pump and nozzle arrangement. A steering deflector mounted at theoutlet of the nozzle can direct the stream substantially laterally inrelation to the longitudinal axis of the vessel to provide steering. Areverse duct mounted astern of the steering deflector can direct thestream substantially ahead along the longitudinal axis to providereverse. One to four or more propulsion units may be installed acrossthe stern according to size of a particular vessel or a configurationdesigned for the vessel. A bow thruster may also be used to assist somemanoeuvres.

Engine power levels and the reverse ducts are conventionally controlledusing lever systems which vary the ahead and astern thrust of eachwaterjet in both magnitude and direction. A single lever often controlsboth the throttle and the position of the duct. With the lever in acentral position the engine idles and the duct is partially down toproduce zero net thrust. Moving the lever forwards or backwardsinitially raises or lowers the duct at constant throttle, and then opensthe throttle, to create a range of thrust levels directed ahead orastern. Separate levers may also control the throttle and duct for eachunit although this can be cumbersome for the operator.

Steering may be controlled in various ways. Some waterjet units haveindependent steering deflectors and reverse ducts, in which case thesteering deflectors on all of the units in an installation are generallycontrolled synchronously by way of a helm wheel or steering joystick.Other units have the reverse ducts mounted on the steering deflectorsand their operation is not independent, in which case the steeringdeflectors on each of the waterjets in an installation may not becontrolled synchronously. The control requirements of these twoalternative systems are generally different.

Rotation and forward or backward translation of a vessel having multiplewaterjet units is usually straightforward using existing controlsystems. However, a sideways manoeuvre into a berth for example, can beawkward or counterintuitive even for experienced operators. U.S. Pat.No. 5,031,561 describes a relatively complex system for a vessel havingreverse ducts mounted on the steering deflectors. The system involvestwo modes in which the steering deflectors are operated synchronouslywhen underway but differentially for many manoeuvres.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide control systemswhich are relatively simple and intuitive to use by operators ofparticular vessels propelled by waterjets, or at least to provide analternative to existing systems. The invention generally involvesprovision of a dual axis joystick for control of reverse ducts onpropulsion units in which the reverse ducts are mounted independently ofthe steering deflectors.

Accordingly in one aspect the invention may broadly be said to consistin a thrust control system for a water-borne vessel having port andstarboard waterjet propulsion units comprising: thrust reverse meanswhich determines respective deflections of thrust for the propulsionunits, and first manual control means having two degrees of freedomwhich actuates the thrust reverse means to cause either common ordifferential deflections of thrust for the propulsion units.

Preferably the system includes thrust steering means which determinescommon deflections of thrust for the propulsion units, and second manualcontrol means having one degree of freedom which actuates the thruststeering means. The system may also include a thrust power means whichdetermines power levels for the propulsion units and which may also beactuated by the first manual control means. The manual controls and themeans which they actuate may be provided in newly constructed vessels oras modules for upgrade of systems on existing vessels.

In a second aspect the invention may broadly be said to consist in acontrol system for a water-borne vessel having port and starboardwaterjet propulsion units comprising: thrust power means whichdetermines operational power levels for each of the propulsion units,thrust steering means which determines a common deflection of thrust foreach of the propulsion units during all steering operations, thrustreverse means which determines further deflections of thrust separatelyfor each of the propulsion units, first manual control means whichactuates the thrust reverse means, second manual control means whichactuates the thrust steering means, and third manual control means whichactuates the thrust power means.

The invention also consists in any alternative combination of parts orfeatures here described or shown in the accompanying drawings. Allequivalents of these parts or features are included whether or notexplicitly set out.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will be described with respect tothe accompanying drawings, of which:

FIG. 1 schematically shows a possible arrangement of propulsion unitsand manual controls and control interfaces on a waterborne vessel,

FIG. 2 indicates a range of fundamental manoeuvres which are possiblewith an arrangement of FIG. 1,

FIG. 3 illustrates a sideways manoeuvre to port for a twin unit systemaccording to the invention,

FIG. 4 is a flowchart showing operation of the controls when actuatingthe propulsion units, and

FIG. 5 shows details of the derivation of water jet actuator signalsfrom joystick signals.

DETAILED DESCRIPTION OF THE INVENTION

Referring to these drawings it will be appreciated that the inventioncan be implemented in a wide range of forms on a wide range ofwaterborne vessels. Details of the vessels, the individual controlcomponents and the propulsion units will be well known to a skilledreader and need not be given here.

FIG. 1 is a schematic diagram showing two waterjet propulsion units 9for a vessel and elements of possible control systems according to theinvention. The waterjet units are typically placed port and starboard atthe stem of the vessel. Three, four or possibly more units may becontrolled together. Each unit has a housing containing a pumping unit11 driven by an engine 10 through a driveshaft 12, a steering deflector13 and a reverse duct 14. In this case the reverse ducts are each of atype that feature split passages to improve reverse thrust and affectsteering thrust to port or starboard when the duct is lowered into thejet stream. The steering deflectors pivot about generally vertical axes15 while the reverse ducts pivot about generally horizontal axes 16independently of the deflectors. Actuation of the throttle, steeringdeflector and reverse duct of each unit is caused by signals receivedthrough control input ports 17, 18, 19 respectively.

The control system in FIG. 1 includes a range of possible components 20located on the vessel for manual use by an operator. Various componentsmay be selected for an entirely new control system, or added to upgradean existing system as required in a particular embodiment. A dual axisjoystick 21, or other controller having two or perhaps more degrees offreedom, is generally provided for operation of the reverse ducts andpossibly also the throttle. A throttle control lever 22 may be providedwhere this function is not included with the joystick. The levertypically allows independent or joint actuation of the throttle on eachunit. Steering input is generally provided manually by way of a steeringlever or joystick 23 or a helm wheel 24 having a single degree offreedom. Steering functions are normally actuated independently of thejoystick 21 but when manoeuvring sideways may be actuated automaticallyaccording to operation of the joystick.

Various other components are also generally provided in a control systemsuch as shown in FIG. 1. Each of the manual controls are usuallyconnected through a panel module 30 via an interface module 32 to atleast one actuator module 31. A number of modules may be linked asrequired depending on the number of waterjet units 9. A display may alsobe included, in the panel module 30 to provide control statusinformation for the operator. The modules interpret manual operation ofthe components 20, such as x,y orientation of the joystick 21 or angularorientation of the wheel 24, and generate actuation signals for thewaterjet units which are input through ports 17, 18, 19.

FIG. 2 shows eight basic manoeuvres of a vessel which may be enabled bya control system having a dual axis controller 21 according to theinvention. These include four translations 1,2,7,8 in which the vesselmoves ahead, astern, to port or to starboard respectively, whilemaintaining a constant compass heading. FIG. 2 also shows four rotations3,4,5,6 in which the vessel turns to port or starboard about a point inthe bow and to port or starboard about a point in the sternrespectively. Manoeuvres resulting from operation of the joystick 21 toposition the reverse ducts and operation of the helm to position thesteering deflectors are shown, in each case with reference to a key. Thesteering deflectors are actuated in synchronism while the reverse ductsare operated in synchronism or differentially as summarised in the tablebelow. Virtually any movement of the vessel may be achieved by acombination of these basic manoeuvres. The control system is intended toallow an operator to use the joystick and/or other controls in a simpleintuitive fashion to cause movement of the vessel. TABLE 1 SUMMARY OF 8BASIC VESSEL MANOEUVRES Port Jet Starboard Jet Reverse Steering ReverseSteering No. Type of manoeuvre Duct Deflector Duct Deflector 1Translation-ahead Up Centre Up Centre 2 Translation-astern Down CentreDown Centre 3 Rotation about bow-port Zero Speed Port Zero Speed Port 4Rotation about bow-stbd Zero Speed Stbd Zero Speed Stbd 5 Rotation aboutstern-port Down Centre Up Centre 6 Rotation about stern-stbd Up CentreDown Centre 7 Translation-port Down ½ Stbd Up ½ Stbd 8 Translation-stbdUp ½ Port Down ½ Port

In one preferred embodiment a control system having a joystick 21 can beused to replace a relatively cumbersome combination of single levers,with or without a separate throttle control. Moving the joystick aheador astern synchronises the reverse and throttle demands and the effectis the same as operating a vessel with a single waterjet in manoeuvres1,2. Moving the joystick transversely controls the port and starboardwaterjets to produce differential thrust. One jet produces ahead thrustwith the reverse duct raised while the other produces astern thrust withthe reverse duct lowered. This rotates the vessel about the stern inmanoeuvres 5,6 in a way which is preferably arranged to occur in accordwith the direction of movement of the joystick. Turning the helm tocounteract the rotation causes the vessel to translate sideways inmanoeuvres 7,8. There is no requirement to change operating modesbetween manoeuvring and traveling at speed as the action of the joystickand helm remain the same throughout.

FIG. 3 schematically shows a vessel 40 with a twin waterjet arrangementand a manual control system according to the invention. A sidewaysmanoeuvre to port is in progress, such as manoeuvre 7 indicated in FIG.2. Nozzles 41, steering deflectors 42 and one of the reverse ducts 43are shown at the stern of the vessel to indicate the port and starboardwaterjets. The reverse duct on the starboard waterjet is not positionedto deflect the water flow from that jet and has been omitted from view.A dual axis joystick 21 and wheel helm 24 are shown forward on thevessel to indicate the manual control system. The joystick has beenpushed to port by the operator and the wheel has been turned tostarboard. This produces jet streams 44 from the waterjets andconsequently thrust vectors 45. The net sideways force acts at a point46 towards the centre of the vessel represented by a thrust vector 47.

FIG. 4 outlines a routine followed by software in the panel module 30when receiving input from the manual controls. The module is continuallymonitoring x,y orientation of the joystick 21 which is generated as apair of signals Jx, Jy. A signal representing the orientation of thehelm has not been shown. In step 50 the module determines demands forport throttle and reverse using functions F1 and F2. In step 51 themodule determines demands for starboard throttle and reverse. The portand starboard waterjet units are actuated accordingly through demandssent to the actuator modules 31.

In one preferred embodiment the control system includes a steeringoffset which may be initiated in step 52 of FIG. 4. This actuates thewaterjet units automatically to create sideways translation of thevessel in manoeuvres 7,8 as if the helm had been used to counteractrotation as described above. Step 53 determines the steering offsetdemand for both port and starboard deflectors according to the yorientation of the joystick 21.

FIG. 5 shows the functionality of the control system, for example themodule 30 shown in FIG. 1, and particularly the derivation from thejoystick signals of the actuator signals used to control the waterjets.FIG. 5 shows various functions as provided by discrete units but in apreferred embodiment the functions are provided by software equivalents.The control system interprets the position of the manually operatedcontrols, in this case the xy orientation of a dual axis joystick, andgenerates actuation signals for the engine throttles, steeringdeflectors and reverse ducts. The joystick provides, to input port 61,an Ahead/Astern signal (Jx in FIG. 4) which signal is indicative of theposition of the joystick on the fore and aft axis. The joystick alsoprovides, to input port 62, a Port/Starboard signal (Jy in FIG. 4) whichsignal is indicative of the position of the joystick on the transverseaxis.

The Ahead/Astern signal and the Port/Starboard signal are summed in anaddition module 63 which outputs the summation result as a Port Inputvalue. A Port RPM Demand signal, provided at output port 65, is derivedfrom the Port Input value by a function module 64 with an input/outputfunction F1 that provides an increase in the Port RPM Demand signal,from an initial low RPM or ‘engine idle’ value, as the modulus, orabsolute value, of the summation result increases above a predeterminedthreshold. In the system shown in FIG. 1, the Port RPM Demand signal isapplied to input port 17 of the throttle control for the port engine 10.

A Port Reverse Duct Demand signal is provided at output port 67. ThePort Reverse Duct Demand signal is derived from the Port Input value(resulting from the summation of the Ahead/Astern and Port/Starboardsignals) by a function module 66 with an input/output function F2 thatprovides an increase in the Port Reverse Duct Demand signal as thesummation result increases, up to predetermined maximum values ofpositive and negative Port Reverse Duct Demand signals. In the systemshown in FIG. 1, the Port Reverse Duct Demand signal is applied to inputport 19 for controlling the port reverse duct 14.

The Port/Starboard signal is subtracted from the Ahead/Astern signal insubtraction module 68 which outputs a Starboard Input value. A StarboardRPM demand signal, provided at output 70, is derived from the StarboardInput value in a function module 69 with an input/output function F1that provides an increase in the Starboard RPM demand signal, from aninitial low RPM or ‘engine idle’ value, as the modulus, or absolutevalue, of the subtraction result increases above a predeterminedthreshold. In the system shown in FIG. 1, the Starboard RPM demandsignal is applied to input port 17 of the throttle control for thestarboard engine 10.

A Starboard Reverse Duct Demand signal is provided at output port 72.The Starboard Reverse Duct Demand signal is derived from the StarboardInput value (resulting from the subtraction of the Ahead/Astern signalfrom the Port/Starboard signal) by a function module 71 with aninput/output function F2 that provides an increase in the StarboardReverse Duct Demand signal as the subtraction result increases up topredetermined maximum values of positive and negative Starboard ReverseDuct Demand signals. In the system shown in FIG. 1, the StarboardReverse Duct Demand signal is applied to input port 19 for controllingthe starboard reverse duct 14.

The control system may also include output ports 73, 74 at which Portand Starboard Steering Deflector Offset Demand signals are respectivelyprovided. As shown in FIG. 5, Port and Starboard Steering DeflectorOffset Demand signals are independently derived from the Port/Starboardjoystick signal in respective function modules 75, 76 each having adirectly proportional input/output function F3. In the system shown inFIG. 1, the Port and Starboard Steering Deflector Offset Demand signalsare applied to respective input ports 18, in addition to the steeringdemand signals generated from the helm control, for controlling the portand starboard steering deflectors 13.

1. A waterjet propulsion system for a water-borne vessel, including:port and starboard waterjet propulsion units, thrust steering meansassociated with the port waterjet propulsion unit(s) and thrust steeringmeans associated with the starboard waterjet propulsion unit(s) fordeflecting the waterjet from the propulsion(s) unit for steering thevessel, which thrust steering means are linked for common steeringmovement together, thrust reverse means associated with the waterjetpropulsion units for reverse deflecting the waterjets from thepropulsion units and which thrust reverse means are mountedindependently of the thrust steering means, and control means operableto actuate the thrust reverse means to cause either common ordifferential deflections of thrust from the propulsion units and tocontrol the thrust steering means.
 2. A system according to claim 1further including: third control means for controlling the power levelsof the propulsion units.
 3. A system according to claim 1 or claim 2wherein a control means is responsive within a first degree of freedomto determine a common deflection of reverse thrust for the port andstarboard propulsion units, and within a second degree of freedom todetermine different deflections of reverse thrust for the port andstarboard units.
 4. A system accordingly to claim 3 wherein the firstcontrol means actuates the thrust steering means while actuating thethrust reverse means to cause port or starboard translational movement.5. A system according to anyone of claims 1 to 4 wherein the thruststeering means maintains a common deflection of thrust for thepropulsion units during translational movements transverse to thevessel.
 6. A system according to anyone of claims 1 to 4 wherein thethrust steering means maintains a common deflection of thrust for thepropulsion units during all movements of the vessel.
 7. A systemaccording to anyone of claims 1 to 6 wherein the control means includesa multiple axis joystick.
 8. A system according to any one of claims 1to 7 wherein the thrust reverse means includes deflector buckets whichare lowerable into the waterjets from the propulsion units for reversedeflecting the waterjets.
 9. A system according to any one of claims 1to 7 wherein the thrust reverse means includes deflector buckets whichare lowerable into the waterjets from the propulsion units for reversedeflecting the waterjets and wherein the deflector buckets are split ordouble cavity deflector buckets.
 10. A system according to any one ofclaims 1 to 9 wherein the thrust steering means include a deflectornozzle associated with the waterjet propulsion units.
 11. A systemaccording to anyone of claims 1 to 9 wherein the thrust steering meansinclude deflector nozzle associated with the waterjet propulsion units,which deflector nozzles are mechanically linked for said common steeringmovement together.